“…To obtain a specification fit for the purpose, we begin with the common empirical approach used for the EKC specification (see [ 5 ], for a comprehensive EKC survey), which is as: where CO 2 emissions present environmental degradation, is the per capita real GDP that positively influences CO 2 emissions up to a certain limit [ 15 ], is the squared of the per capita GDP and it negatively affects CO 2 emissions [ 14 , 70 ], refers to energy use, is trade openness, and is population growth. However, some studies, such as [ 31 , 71 , 72 ]; and [ 73 ] have employed ecological footprints and trade-adjusted carbon emissions as proxies for environmental degradation. For three reasons, this study uses CO 2 emissions instead.…”